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TECHNOLOGY – AEROBYTES Dallara F3 Front wings 0.75


0.65 0.7


0.55 0.6


0.45 0.5


0.35 0.4


0 0.333 0.666 % of max flap angle


Figure 1: the Dallara F3 front lift coeffi cients plotted against four fl ap positions covering the available adjustment range


0.999


2011 2012


25 30 35 40 45


0 0.333 0.666 % of max flap angle


Figure 2: the Dallara F3 ‘%front’ plotted against four fl ap positions covering the available adjustment range


Table 3: the 2011 F308’s aerodynamic data over the range of front wing fl ap adjustment


Flap posn CD -CL -CLf -CLr %front -L/D


Maximum 0.636 1.455 0.549 0.906 37.7 2.288 2/3 1/3


0.631 1.445 0.515 0.930 35.6 2.290 0.624 1.403 0.455 0.948 32.4 2.248


Minimum 0.620 1.333 0.363 0.970 27.2 2.150 Total ∆


-16 -122 -186 +64 -10.5 -139


Table 4: the 2012 F312’s aerodynamic data over the range of front wing fl ap adjustment


Flap posn


The F312’s front wing features a larger main element chord and larger fl ap area than the previous car’s


CD -CL -CLf -CLr %front -L/D


Maximum 0.630 1.591 0.711 0.880 44.7 2.525 2/3 1/3


0.623 1.550 0.660 0.890 42.6 2.488 0.614 1.479 0.577 0.902 39.0 2.409


Minimum 0.606 1.391 0.474 0.918 34.1 2.295 Total ∆


-24 -200 -237 +38 -10.7 -230


have also added greater capacity for front downforce generation and improved overall effi ciency. The F312 front wing is


different in a number of respects from the previous car’s, but with the same range of available adjustment on its larger and more complex fl ap. Figure 1 illustrates how it performed relative to the previous car’s front wing, which had changed little over the years. Clearly, the 2012 car


The F308 wing dates back several years, although some teams did add additional fl aps inboard and ‘bridge’ fl aps


But, with its more potent


front wing, the F312 was not aerodynamically balanced with the wings at maximum angle at both ends of the car, with over 44 per cent of total downforce being exerted on the front axle, compared to a weight split of around 40-41 per cent. Table 2 shows a comparison of the 2011 car in the same confi guration as above with the 2012 car with a reduced front wing angle that gave approximately the same aerodynamic percentage on the front axle.


52 www.racecar-engineering.com • July 2012 In these confi gurations,


the two cars had not only roughly equal balance but also very similar total downforce. And at this comparable level of downforce, the 2012 car generated 3.6 per cent less drag, which calculated to an effi ciency (-L/D) value 3.7 per cent higher than the 2011 car. So, despite the loss of all except one of the various bargeboards and turning vanes, Dallara seems not only to have more than recovered the lost downforce these devices would have helped generate, but


shows greater front downforce across the range of front fl ap adjustment. It also shows greater linearity to the two thirds full fl ap point. That is, it tails off more slowly, which suggests its front wing was further from its stall angle in the wind tunnel at this setting than was the F308’s wing. And, because the F312’s is a more potent front wing, the changes in downforce between the same adjustment increments were somewhat larger. Fortunately, Dallara provides


a wide range of adjustments in between the settings illustrated here, and no Gurneys were available at test time, which


would provide further fi ne tuning. Figure 2 illustrates the effect on aerodynamic balance (%front) of adjusting the front wings. Tables 3 and 4 show full sets


of data obtained at the four front fl ap angles tested on each car at maximum rear wing angle, and give a clearer idea of how the cars compared over the front wing adjustment range. Most of the trends are as expected, but one of the more interesting ones is that the increase in –CLr with decreasing front wing fl ap angle was considerably less on the 2012 car, despite the front wing being more potent and further ahead of the front axle on that car. This suggests the F312’s front wing also has less adverse aerodynamic effect on its rear wing and / or other rear downforce-generating devices than was the case with the F308. Note too, as has been


previously highlighted in this column, that front wing adjustments do not make large changes to the overall drag value. Racecar Engineering’s thanks


to Fortec Motorsport 0.999 Dallara F3 Front wings


2011 2012


-­‐CLf


%Front


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